EFFECT OF CORTICOSTEROIDS ON FREE AND SULFOCONJUGATED CATECHOLAMINES AT BIRTH IN PREMATURE NEWBORN SHEEP

We previously demonstrated that prenatal corticosteroids attenuated th e expected exponential increase in circulating catecholamines at birth . The present studies were undertaken to determine if alteration in su lfoconjugation could account for this attenuation. Catheterized fetal lambs received saline (n = 6) or corticosteroids (n = 8) intravenously for 60 h. The lambs were delivered by cesarean section at 130 +/- 1 d ays gestation. Ventilatory and cardiovascular responses and plasma cat echolamine concentrations were measured for 2 h after birth. Although plasma free catecholamines levels were higher in controls than in cort icosteroid-treated fetuses, the sulfoconjugated levels were similar in the two groups. Thus the corticosteroid-treated fetuses had a higher proportion of plasma sulfoconjugated catecholamines consistent with th e possibility that sulfoconjugation was augmented during intrauterine life. After birth, the corticosteroid-treated animals showed an attenu ated increase in plasma free catecholamine levels compared with contro ls but a similar increase in sulfoconjugated catecholamine levels to t he control animals. The proportion of plasma sulfoconjugated catechola mines was higher in the corticosteroid-treated animals; however, the i ncrease in sulfoconjugated catecholamines was insufficient to account for the attenuated overall increase in total catecholamines in the cor ticosteroid-treated animals.